Detection and Determination of Ethylene
Glycol in Lubricating Oil H. LAAIPRET, E. E. SOMMER, AND A. D. KIFFER Kational Carbon Company, inti-Freeze Research Dipision, Tonawanda, N. Y.
A method is described for the detection of ethylene glycol in crankcase oil based on isolation of the ethylene glycol by distillation, and identification by means of physical properties. The test is specific for ethylene glycol and can be made quantitative i n the absence of other high-boiling antifreezes, as is usually the case.
T
HE analysis of automobile crankcase oil for antifreeze
materials is sometimes necessary in order to determine if leakage of engine cooling solution into the crankcase has occurred. Such analyses are important in determining whether antifreeze materials bring about crankcase sludge formation as much as does water alone. The most common antifreeze materiala in use today are methanol, ethanol, and ethylene glycol, although glycerol, diethylene glycol, propylene glycol, iqopropanol, inorganic salts, sugars, and glycol derivatives are also used t o a certain extent. TThile specific methods for the identification of methanol and ethanol in oil are known (4), no satisfactory procedure has been described which may be used for the specific detection or determination of ethylene glycol in crankcase oil. The spot test of Feigl (2) responds to other polyhydric alcohols such as glycerol, and even to oil decomposition products, as shown by the authors' tests; tests relying on the oxidation of ethylene glycol to oxalic acid (4, 5 , 7 ) also give positive reactions with other polyhydric alcohols, and this procedure is further complicated by the fact that oxalic acid mzy be present in the oil, since it is used as a cooling system cleaner; the mercuric iodide method of Fleury and Marque (3) is quantitatively accurate under certain conditions but cannot be used for qualitative tests owing to itb complete lack of specificity. Other methods described in the literature have been investigated by the authors and found unsatisfactory. TABLE I. PHYSICAL PROPERTIES OF ANTIFREEZELIQEIDS Substance
Refractive Index
SPCClfiC Gravity, 20' C / 2 0 ° C
Boiling Point, O
C
To circumvent the difficulties met with in these cheniical tests, they employ the fundamental method of isolating the antifreeze component from the oil ant3 identifying the material by means of itmsphysical properties. The glycol is separated from the oil by a xylene distillation, the distillate is fractionated, and the boiling point, specific gravity, and refractive index of the ethylene glycol fraction thus isolated are determined. Procedure To a 100-ml. sample of the oil to be tested 100 ml. of xylene are added, and the mixture is distilled for 2 hours according to A. S. T. M. Designat'ion D95-30, using the apparatus described ( 1 ) . One gram of sodium carbonate should be added to the oil before the distillation if any calcium chloride or oxalic acid is detected.
I t is desirable to add the sodium carbonate only if the calcium chloride or oxalic acid is detected, since this addition prolongs the time of distillation. The lower, aqueous layer of the distillate is fractionated in a small column to separate the ethylene glycol from water and other materials, using microequipment (6) if the ethylene glycol concentration proves low. If only one high-boiling antifreeze material is present, as is usually the case, this is immediately evidenced by the distillation. If the distillation indicates the presence of more than one highboiling antifreeze, it may be necessary to resort to a series of careful microfractionations in order to separate the ethylene glycol fraction, but fortunately this is rarely the case. In either event, the ethylene glycol is finally identified by determining the specific gravity and refractive index of the fraction boiling in the range 195' to 200" C. (Table I). Thevolumeof ethylene glycol is sometimes SO small that standard microtechnique must be used to determine the specific gravity. The entire method may be made quantitative, in case only one high-boiling antifreeze is present in the distillate, by measuring the volume and refractive index (or volume and specific gravity) of the aqueous solution obtained from the xylene distillation (cf. Table 11, unpublished data). TABLE 11. PHYSIC-~L PROPERTIES OF AQCEOUS ETHYLENE GLYCOL SOLCTIOSS Weight
Specific Gravity, 150 c./150 1.0132 1.0272 1.0411 1.0550 1.0686 1 0812 1.0924 1.1026 1,1111
Refractive Index (20' C.) 1,3130 1 3525 1 3626
c.
%
10 20 30 40
%50 60 70 80 90
1 R72R
1 3828 1.3930 1 4033 1.4136
1 4239
If more than one high-boiling antifreeze is present in the distillate, this quantitative method cannot be used, but the approximate glycol content can still be ascertained by measuring the volume of the ethylene glycol cut during the subsequent' microfractionation.
Results To demonstrate the reliability of the qualitative method, samples of fresh and used lubricating oil cont'aining known amounts of ethylene glycol were analyzed. The following antifreeze materials and contaminants have been shown not to interfere with the method: calcium chloride, oxalic acid, glycerol, sugar, and diethylene glycol. These tests were made IT-ith twice as much interfering substance as ethylene glycol present. Later t'ests have shown that ethylene glycol may be positively identified in the presence of much larger quantities of propylene glycol, diethylene glycol, and methyl and ethyl Cello3olves. In these tests as little as 0.15 per cent of ethylene glycol was detected in the oil. I n general, the sensitivity of the method may be further increased by taking larger than 100-ml. samples of the oil for distillation. OIL FOR ETHYLENE TABLE111. ANALYSISOF LUBRICATISG GLYCOL Oil S a m p l e Taken
Ethylene Glycol Added
CC.
Grama
100 100 100 100 100 100
3 5 5 0 0 0
30 36 30 112
107 00
Ethylene Glycol Recovered B y specific By refractive gravity index Grrcru
3 .4
5 1 5 4 0.10 0.10 0 00
Grama
?.! a a 5 4 0.10 0.10 0.00
ANhLYTIChL EDITION
SEPTEMBER 15, 1940
T o demonstrate the accuracy of the quantitative method, representative results are given in Table 111 for both new and used oils, to which aqueous glycol solutions were added in the amounts indicated. This quantitative determination is possible only in the absence of high-boiling antifreezes other than ethylene glycol.
Literature Cited (1) Am. Soc Testing hfateiials, "Standards on Petroleum Products and Lubiicants", p 345, Philadelphia, .Imerican Society for Testing Materials, 1937.
527
( 2 ) Feigl, F., "C2ualitative .$nalysis h y Spot Tests", 1st ed., pp.
251-3, New l o r k , Sordemann Puhlishing Co., 1937. (3) Fleury. P., and Marque, J.. J . pharm. c h i m . , (8) 10, 241-57 (19"). (4) L e i i n , H . , Uhrig. K., and Stehr, E.. ISD. Esu. CHEM.,Anal. Ed.. 1 1 , 134-6 (1939). (5) Middleton, -1. W., Analyst, 59, 522 (1934). (6) Morton. -1.A,. "Laboratory Technique in Organic Chemistry", 1st ed., pp. 50-1, 73, 74, Kew York, McGraw-Hill Book Co., 1938. (7) Rosenthaler, L., "Der Nachxveis organischer Verbindungen", p. 104, Stuttgart, Ferdinand Enke, 1926.
Nomograph for Correction of Lactometer Readings and Calculation of Milk Solids LINCOLS RI. LAMPERT Dairy Service Laboratory, State Department of .4griculture, Sacramento, Calif.
I
S T H I S country the routine calculation of the solids-notfat or of total solids in a sample of milk usually is made by means of a formula based upon the Babcock fat test and a Quevenne lactometer reading. The simplified Babcock formula ( I O ) generally is used, in which
Solids-not-fat =
lactometer reading at 60" F. 4
per cent fat $
5
A statistical study (6) of this formula showed that its accuracy increases as the number of cons contributing to the milk is increased. The estimation, however, is only approximate, and its use as such is understood by milk inspection departments and dairy officials. Variations from gravimetric results for the solids-not-fat may deviate b y 0.2 per cent or more. Investigations have shown that the physical state of the fat globules in the milk affects its density, and for the most accurate work this characteristic of the fat globules must be taken into consideration. Bakke and Honegger ( 1 ) made a thorough investigation of this problem and devised a method for securing a uniform basis for the comparison of lactometer readings. Their method, which has been overlooked by many American investigators, is to heat the milk to 40" C. (104" F,), cool to 15" C. (59" F.), and make the lactometer reading as usual. By this method consistent results are obtained on a sample of milk, whether it i. frebli, has been held a t room temperature or in a refrigerator, or has been subjected to various degrees of agitation. Kithout this preliminary treatment, the same milk gives widely different lactometer readings under these diverse conditions. Hoyt, Lampert, et 01. (4) corroborated these findings and pointed out other factors involved in the use of the lactometer. This and other work was recently reviewed by Lampert (6). Sharp and Hart (9) recommend that density readings be made when the fat globules are in the liquid state. According to their method, the milk is heated to 45" C.(110" F.) for 0.5 minute, and cooled to 30" C. (86" F,), and the tot;ll solids are estimated from the specific gravity according to the equation lactometer reading Total solids = 1.2537 fat 0.2680 sp. gr, of milk
+
It is generally conceded that the only reason for the use of the lactometer is the speed and conT-eniencewith which a very good approximation of the solids content may be obtained Long usage has established the Babcock formula, and pub-
lished data show that the results obtained with it are as satisfactory as those obtained with the other more complicated procedures, which, theoretically a t least, appear more valid. Sharp and Hart found that their calculated and gravimetric determinations may differ by 0.30 per cent and Hoyt, Lampert, et al. (4) found that the Bakke and Honegger method on mixed herd milk varied between +0.13 and -0.26 per cent from gravimetric results. Most textbooks and manuals ( 2 ) contain tables that serve to eliminate the calculation required b y the Babcock formula. Two sets of tables are needed, since the lactometer reading often is not made a t exactly 60" F. and therefore requires a correction, The second table gives the solids-not-fat corresponding to a given lactometer reading a t GO" F. These tables take into consideration the fact that the corrections involved vary with the temperature a t which the lactometer reading is made as well as with the specific gravity of the milk. At least three different slide rules have been macle for this calculation, but they are not in common use. One of these, Richmond's "milk scale" (S),is based upon a formula not often used in the United States since it gives results 0.14 per cent higher than those obtained by Babcock's formula. I n general, slide rules and tables give corrections for temperatures ranging from about 35" to 80" F., but the preferred practice is to obtain a lactometer reading a t a temperature of between 55" and 65" F. As far as the writer has been able to learn, no nomograph has been devised to replace the use of tables. Such a nomograph would have decided advantages, especially when many calculations are to be macle. The nomograph is easier and quicker to read than tables and eliminates the interpolations needed to obtain the corrections if the lactometer is read t o parts of a whole degree or if the fat reading is made to less than 0.1 per cent, the limit in most tables. T o this end, the nomograph illustrated was constructed and has been found very satisfactory. Since the nomograph is constructed from data in the tables, it cannot give results more accurate than those in the tables or obtained by formulas vhich in themselves are based upon the average analysis of many samples of milk. The principal advantages in its use are facility and speed and the fact that it may be printed on a single page. I n using the nomograph, two readings must be made by means of a straightedge, or better, a transparent celluloid guide with a line drawn down its length. First the lactometer
